This invention relates to a telescope apparatus for elevated orientation of a working platform or other operating or support structure.
Lift devices are widely used for locating of personnel in raised work areas in both industrial, institutional, municipal applications. Generally, such devices include a mobile support structure for moving of the device to the area of work. An elevating mechanism is mounted on the support with a work platform supported thereby. The lift mechanism usually includes various mechanically collapsible mechanisms and powered positioning motor means. For transport, the mechanism is collapsed to locate the mechanism and platform on the base support for convenient and reliable transport. At the work area, the lift mechanism is actuated to raise the platform to the elevated work area. Various mechanisms have been developed and are commercially used in commerce. Typically, such mechanisms use various scissors mechanism with multiple linkages, a plurality of individual articulated boom members connected for successive alternate angular extensions and collapsing and the like. In addition, a telescopic boom unit provides a convenient and reliable mechanism in a lift device for many applications. The telescopic boom unit is formed with a base member pivotally mounted to the support unit and one or more outer telescopic members. A motor means is coupled to the telescopic section for extending and retracting the telescopic boom unit. The platform is pivotally secured to the outermost tip boom member, and may be secured with one or more articulated boom members secured between the platform and telescopic boom unit. In the transport or storage position, the telescopic boom unit is collapsed and pivoted onto the base support unit. In a lift or raised position the boom unit is pivoted upwardly, generally with a slight angle to the vertical and the telescopic boom extended. In the various systems, the motor means are separate hydraulic cylinder units for pivoting the boom unit and for expanding and contracting the telescopic members in a controlled manner for smooth, reliable positioning of the platform or other work support structure. Thus, separate hydraulic cylinder units are provided for collapsing the platform to the transport position and for locating and maintaining the platform in appropriate horizontal orientation in the raised position.
In telescopic boom and other articulated boom apparatus, the horizontal orientation of the platform will vary with the angular orientation of the boom unit because of the pivotal mounting of the platform to the tip of the boom and for complete collapse of the unit in the lowered position. The separate hydraulic cylinder unit or units may be provided between the tip boom member and the platform support for establishing and maintaining precise location of the platform for safe operating usage by the supported personnel. In systems using articulated boom members, a vertical post at the articulated connection is desirable to maintain the orientation of the boom members. An additional cylinder unit may be used to control the vertical orientation of the vertical post. Typical telescopic boom units are shown in U.S. Pat. No. 4,754,840 which issued Jul. 5, 1988 and U.S. Pat. No. 4,775,029 which issued Oct. 4, 1988.
The hydraulic supply to the various cylinders is generally manually controlled by an elevator operator, with separate controls of the elevating apparatus, as well as the platform structure. The structures must therefore be of a very substantial and rugged construction. Generally this requires use of heavy metal structures creating substantial weights and forces.
The over-reach of the apparatus or mechanisms relative to the base support structure creates significant over turning forces. This requires careful and effective design of the elevating mechanism in relationship to the support structure to prevent creation of a hazardous condition with the platform in an elevated position. In addition, in the collapsed position the elevating mechanism and platform should be appropriately aligned on the support structure to permit the convenient and safe transportation of the device. Thus, the platform should be centrally located on the base support unit to establish optimum distribution of the weight and forces during the transport.
Mechanical leveling of the platform and vertical support structure have been suggested by using parallelogram linkage structures interconnected between individual boom sections in various scissors and multiple articulated boom devices. Typical examples of parallelogram linkage structures are, for example, shown in Canadian Patent 990,224 which issued Jun. 1, 1976 and U.S. Pat. No. 4,935,666 which issued on Sept. 4, 1990. In such structures, a parallel arm is mounted to the boom section and interconnects through end linkages to the corresponding section and an adjacent section such that the movement of one section is transmitted to an adjacent section to maintain a predetermined angular relationship between the several sections, with an outer end section having an end support for the appropriate horizontal orientation of the platform.
In telescopic boom apparatus, a single boom unit may be used with the boom angular orientation varied by and set by the pivoting hydraulic cylinder unit. In such systems, the separate hydraulic leveling cylinder units are used to orient and maintain the proper orientation of the platform. Multiple hydraulic cylinder units require close coordination between the operation of the cylinder units. Further, hydraulic systems have various inherent disadvantages from the standpoint of possible small leakages, which can destroy synchronized movements. Normal wear in any hydraulic system can also destroy the desired synchronized movements. The hydraulic system thus require continuous maintenance and often require time consuming adjustments by the elevator operator.
In addition, the smooth and controlled movement of the platform is essential to the comfort and safety of the personnel. Such movement is also significant in connection with the minimizing of the forces placed on the elevating mechanism. This again requires relatively skilled control and operation of the lifting and lowering elevator mechanism. Systems have been suggested for minimizing the required hydraulic motors and the like and related controls. Thus, for example, in boom structures having intermediate articulated joints or couplings, gear systems have been provided for providing controlled movement of the gear mechanism in response to the hydraulic motor drive of a boom structure. The mechanical parallelogram interconnection between articulated boom sections have also been suggested.
In telescopic boom systems, however, universal practice has been the provision of the telescoping boom in combination with multiple hydraulic motor units for lifting of a pivotally mounted boom and a hydraulic cylinder motor for positioning and orienting of the platform.
A distinct demand and need exists for a simpler more reliable telescopic boom system which can eliminate the necessity for the multiple hydraulic motors and providing a stable mobile lift assembly for transport and for expanded work positioning.